采用溶血实验、药敏实验、耐药基因和毒力基因PCR扩增对屎肠球菌Ef2进行安全性评估,实验结果表明,屎肠球菌Ef2溶血实验呈阴性,对庆大霉素、链霉素等不敏感,而对万古霉素等其他大部分抗生素抗菌药物敏感,无毒力基因检出,因此初步判定该菌株是安全的,可用作后续实验。通过单因素结合正交实验对该菌株产生物胺氧化酶的诱导培养基和培养条件进行优化,最后确定诱导培养基的最佳成分为:乳糖50 g/L、腐胺6 g/L、酵母膏8 g/L、MgSO4 3 g/L、MnSO4 0.03 g/L、乙酸钠1.5 g/L;最佳培养条件为:初始pH 7.0、接种量0.5%、培养时间36 h、培养温度32 ℃。生物胺氧化酶酶活力从诱导前的10.9 U/mL提升至26.12 U/mL,酶活力提高了139.63%。研究结果表明,通过对培养和诱导条件的优化,可大幅度提升屎肠球菌Ef2产生物胺氧化酶的活力。
Hemolysis tests, antibiotics susceptibility tests, and PCR amplification of virulence genes and drug resistance genes were used to assess the safety of Enterococcus faecium Ef2. The results of hemolysis tests were negative. E. faecium Ef2 was not sensitive to gentamicin and streptomycin, but it was sensitive to vancomycin and most of other antibiotics. No virulence genes were detected, and therefore the strain could be preliminarily determined as safe. The induction medium and culture conditions of producing amine oxidase by this strain were optimized. The optimal components of the induction medium included 50 g/L lactose, 6 g/L putrescine, 8 g/mL yeast extract, 3 g/L MgSO4, 0.03 g/L MnSO4, and 1.5 g/L sodium acetate. The optimal culture condition was as follows: initial pH of 7.0, 0.5% inoculation, cultured for 36 h at 32 ℃. The activity of amine oxidase increased by 139.63% to 26.12 U/mL after induction. The results showed that the activity of amine oxidase produced by E. faecium Ef2 could be greatly increased by optimizing the culture and induction conditions, which lays a foundation for further study on producing amine oxidase by this strain.
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